Marin faces big storm predicted for the weekend

Just last week, weather scientists with the National Weather Service said we're in a La Niña season, meaning there is a good chance Marin will see below-average rainfall totals this season.

It certainly won't seem that way this weekend.

A series of storms packing strong winds is expected to pound the Bay Area beginning as early as Thursday night and could deliver as much as 5 inches of rain to the region, according to the National Weather Service.

Simply put, it's going to be "really, really wet," said Diana Henderson, a forecaster with the National Weather Service.

Point Reyes National Seashore officials issued a warning Wednesday morning, saying the storm might knock down trees along roads and trails as winds could whip as high as 60 mph.

Park staffers were already checking culverts and placing gas-powered generators near wells and buildings in the event of power outages.

In flood-prone communities such as San Anselmo, crews were cleaning culverts and sweeping up leaves, which are often the culprit when storm lines clog. The town is also keeping an eye on the creek for any fallen trees or limbs that may act as obstructions.

"The creek rising has a lot to do with how much rain falls in how short a time and how saturated the ground is," said City Manager Debbie Stutsman. "We have a procedure and will be ready to mobilize."

Farhad Mansourian, county director of public works, said his crews would be ready to deal with a storm big or small.

"We are ready, we know the trouble spots," he said. "We will have to see how bad the intensity of the wind is; that will tell us how we have to adjust our tactics."

In addition to rain Thursday night or Friday morning, Saturday could bring moderate to heavy rain and gusty winds, according to the weather service.

Forecasters are predicting rainfall totals of anywhere from 2 to 5 inches, which could put most areas of Northern California above normal for this time of year.

"What's coming in on Friday is a good amount of rain," Henderson said. "And then you add even heavier stuff on Saturday and Sunday."

The rain could carry over into early next week and potentially cause problems in higher elevations which could receive as much as 10 inches of rain during the next week, according to the weather service.

Although weather scientists are saying we're currently in a La Niña season, conditions that are more likely to produce a drier winter, there is no guarantee the Bay Area will see below-normal rainfall totals.

Since 1950, there have been 19 years with La Niña conditions. In those years, rainfall in San Francisco has averaged 90 percent of normal, and in Los Angeles 80 percent of normal. During the most recent La Niña event, in 2007-08, rainfall was 79 percent of normal in San Francisco.

To understand major climate trends, scientists collect temperature readings every week from dozens of buoys in the Pacific Ocean. They combine them with satellite images and temperature readings from ships, and then plug the data into computer models from scientific agencies around the world.

La Niña conditions are characterized by unusually cold ocean temperatures in the Equatorial Pacific, compared with El Niño, which is characterized by unusually warm ocean temperatures in the Equatorial Pacific.

Currently, water along the equator in the Pacific is between 1.3 and 1.7 degrees Celsius cooler than normal. In extreme La Niña events, it can get up to 4 degrees Celsius, or 7 degrees Fahrenheit, cooler, affecting everything from the frequency of storms to catches of commercial fishers.

Tom Evans, a warning coordination meteorologist for the weather service, said Friday this year's Bay Area rainfall outlook was a "best chance for below normal."

The Bay Area News Group and IJ reporter Mark Prado contributed to this report.